In certain areas water treatment is provided in small scale sewage treatment systems using septic tanks. Septic tanks provide an anaerobic bacterial environment that develops in the tank decomposes or mineralizes the waste discharged therein. Septic tanks can be coupled with other on-site wastewater treatment units such as biofilters or aerobic systems. Periodic maintenance is required to remove the solids which settle and gradually fill the tank.
A septic tank includes a tank in fluid communication with an inlet at one end and a drain at the other end. The tank usually includes two chambers separated by a dividing wall. One chamber allows for solids to settle and scum to float, the other chamber receives the excess fluid and allows for further settlement. Remaining impurities can be eliminated in the soil, with the excess water can be eliminated through a piping network. The entire septic system can operate by gravity alone. Two-stage septic systems provide for sludge to be digested in a separate tank.